The present invention relates to a variable volume type vane pump and, more particularly, to a lubrication art of a cam ring thereof.
A variable volume type vane pump has served as a hydraulic source of an automatic transmission, and the like. Such variable volume type vane pump is described, for example, in Automotive Engineering, extra edition vol. 37, no. 7 published in June 1988 by Tetsudo Nihon Sha Co., Ltd.
Referring to FIGS. 7 and 8, there is shown the variable volume type vane pump as mentioned above. This pump includes a rotor 01, a plurality of vanes 02, and a cam ring 03 which are disposed within a housing 06 with a cover 07. The cam ring 03 is slidably displaced relative to the housing 06 and the cover 07 by a control piston 05 which is operated by a feedback pressure of a pressure regulator valve 04. This changes the eccentric amount of the cam ring 03 to the rotor 01, thus adjusting a discharge of the pump.
In order to prevent seizing of slide surfaces of the cam ring 03 and the cover 07 due to oil lack, the cam ring 03 is formed with a lubricating groove 010 at the side thereof, through which oil passes from an outlet port 08 to an inlet port 09 susceptible to be seized.
Additionally, since the lubricating groove 010 is easy to choke with worn metal and facing powder, same is formed with a drain groove 011 for oil flow.
With such known variable volume type vane pump, lubrication of the cam ring 03 is performed by supplying a part of hydraulic oil discharged from the outlet port 08 to the lubricating groove 010. Passing through the drain groove 011 and an oil reservoir 012, the hydraulic oil is returned to a reserve tank 104 via a drain passage 013.
Accordingly, a part of discharged hydraulic oil is always consumed for lubrication of the cam ring 03, causing large leakage loss of hydraulic oil, resulting in a great decrease in pump efficiency.